Isostatic moulding press



y 16, 1967 D. E. WITKIN 3,319,292

ISOSTATIC MOULDING PRESS Filed Dec. 22, 1965 s Sheets-Sheet 1 IN VENTOR Donald E. \A/Hzkin aw a9 1 ATTORNEYS 6 Sheets-Sheet 5 Filed Dec. 22, 1965 INVENTOR 40 Dana (d E \ll iikin BY 1 2v Pm ATTORNEYS United States Patent 3,319,292 ISOS'IATIC MOULDING PRESS Donald E. Witkin, Warren, Pa., assignor to National Forge Company, Irvine, Pa., a corporation of Delaware Filed Dec. 22, 1965, Ser. No. 515,607 Claims. (Cl. 185) The present invention relates to moulding presses and more particularly to an improved construction for a press of the isostatic type for the manufacture of relatively small components at a high rate of production which involves the basic steps of filling an elastic mould with powdered material and then subjecting the mould to hydrostatic pressure until the powder is compacted into a solid mass.

The conventional method of isostatic pressing consists in filling loose, individual moulds with the moulding material in powder form, closing and sealing these moulds, placing the filled moulds within a pressure vessel, closing and locking the cover of the pressure vessel, pumping up the pressure vessel to the desired hydrostatic pressure by means of an external pump, stopping the pump and venting the pressure vessel to relieve the pressure, unlocking and opening the cover, removing the moulds, pumping out some of the fluid and then emptying the moulded article from the mould. This then completes a moulding cycle which is then repeated.

The improved isostatic pressing apparatus in accordance with the present invention accomplishes all of the foregoing functions, without any need for manual intervention. In addition, no complex mechanical or electrical controls are necessary since all functions for a complete moulding cycle are inherently interlocked and coordinated by virtue of its inherent design. Moreover, no high pressure fittings or tubing connections are required, nor are any high-pressure valves necessary. No external pump is required since the improved isostatic press includes its own self-controlled pump which is of the positive displacement type thus assuring reliable operation and uniform moulding pressure.

It is accordingly a principal object of the invention to provide an improved and automatic isostatic pressing apparatus which is essentially completely mechanical in operation, can be manufactured at relatively low cost, and which has a production rate higher than that obtainable with conventional isostatic pressing equipment.

It is a further object to provide a novel isostatic pressing apparatus which includes a rotatable body member having at least one moulding cavity containing an elastomeric moulding member and a hydrostatic pump of the positive displacement type which includes a piston operating in a cylinder, the cylinder being in fluid communication with the exterior of the elastomeric moulding member so as to develop a radially inward directed isostatic moulding pressure on the mould material, and the piston being operated as the body member rotates by means of a cam follower which engages a cam ring. Preferably the body member includes one or more pairs of moulding cavities and associated hydrostatic pumps displaced 180 apart, and with an inlet hopper for moulding material and a discharge outlet for moulded articles likewise located 180 apart so that one complete moulding operation takes place in each half-revolution of the body member, one moulded article being discharged by gravity from one moulding cavity of one pair at the bottom of the body member while powdered moulding material is being filled into the other moulding cavity of that same pair from a hopper at the top of the body member.

The foregoing as well as other objects and advantages inherent in the invention will become more apparent from the following detailed description of one suitable embodiice ment of the improved isostatic moulding apparatus and from the accompanying drawings wherein:

FIG. 1 is a longitudinal view of the apparatus, with the upper half shown in axial section;

FIG. 2 is a transverse sectional view taken on line II II of FIG. 1;

FIG. 3 is also a transverse sectional view and which is taken on line IIIIII of FIG. 1; and

FIG. 4 is a sectional View across a diameter of one of the moulding cavities, and which is drawn to an enlarged scale to permit a clearer understanding of its details of construction.

With reference now to the drawings, the improved isostatic moulding apparatus is seen to comprise an outer steel casing 10 which has a thick wall and is of a cylindrical configuration and which remains stationary in a horizontal attitude during the moulding operation. This casing is provided at the top with an inlet 11 which serves as a hopper for powdered moulding material. The hopper can remain substantially filled with a volume of powdered moulding material in excess of that of the moulding cavity, or a predetermined amount of the moulding material can be charged through the hopper into the moulding cavity at each filling of the latter. A discharge outlet 12 for moulded articles is provided at the bottom of casing 10 displaced 180 from inlet 11 for gravity discharge of the moulded articles or compacts as they are sometimes called.

Rotatably mounted within casing 16 is a rotor body 13 which is also made of steel. This rotor is provided with one or more pairs of mould cavities 14- which are likewise located l apart. Each mould cavity 14 has a cylindrical configuration and is equipped with such moulding components as are required for moulding an article of the desired configuration. In the illustrated embodiment, the moulding apparatus is set up for moulding a bushinglike body B which requires use of a mandrel or core 15 provided with a threaded stud 15a at one end thereof so as to enable it to be screwed into place at the bottom of the mould cavity. Surrounding mandrel 15 concentrically, and in radial spaced relation therefrom, is an elastomeric moulding member of rubber, in the form ofa sleeve 16 surounded by an annular back-up member 17 which can be made from aluminum. This back-up memher is provided with a plurality of oil-admission channels 18 which extend radially through the wall thereof as can be seen quite clearly from the enlarged detail view in FIG. 4. Also, as shown in this view, the opposite ends of the elastomeric sleeve 16 are turned outwardly over the ends of the back-up member 17 and extend partially between the inner surface of the mould cavity and the outer surface of the back-up member so as to effect a pressure seal between sleeve 16 and rotor body 13. These two surfaces are also incidentally spaced slightly from each other and thereby establish a circular channel 19 from which oil under pressure from the pump, to be later described, is forced through channels 18 into moulding pressure contact with the outer surface of the elastomeric sleeve 16. The configuration of the elastomeric member and its back-up will, of course, be dictated by the configuration desired for the article to he moulded.

As can be seen from FIG. 2, the engaging surfaces 10a and 13a of the outer casing and rotor body respectively are cylindrical while the end surface of the sub-assembly of the elastomeric member and its back-up annulus is fiat. This necessitates use of an annular transition ring 20 which is interposed between the end of the sub-assembly 16-17 and the inner cylindrical surface 10a. The under surface of this transition ring 20 is fiat but its outer surface is arcuate in the plane of FIG. 2 to match the curvature of the arcuate surface 10a. Ring 20 is preferably made from Teflon to reduce the friction as between its surface and the cylindrical surface ltla of the outer casing as the rotor body 13 is rotated.

As seen from FIG. 2, the inlet 11 and outlet 12 have a tapered configuration converging in a radially inward direction and their dimension at the inner surface a is less than that of the outer dimension of the sub-assembly of the moulding components 16, 17 and 29 to prevent drop-out at the lower position. Thus, it is not possible to insert these moulding components with the rotor body already in place inside the outer casing. In order to permit such insertion, so that one moulding sub-assembly can be replaced with another when required so as to change over from one moulded compact to another, casing 10 is provided with another, cylindrical opening 21 in the wall thereof of the same size as the cylindrical mould cavities 14 and which is located intermediate the inlet and outlets 11 and 12. Opening 21 is closed by an assembly comprised of an inner insert 22 which has a cylindrical configuration to match that of the opening 21. The inner end 22a of insert 22 is curved to match the curvature of the cylindrical surface 10a and a flange 22b is provided at the opposite end to establish a shouldered connection with the opening 21 which locates the inner arcuate end of the insert at its proper position. Proper orientation of the insert 22 is established by a dowel pin 23. A removable plug 24 having a threaded portion 24a is threaded into a threaded portion of the opening 21 in order to maintain the insert in place. To replace one subassembly of moulding components with another in the mould cavity, plug 24 and insert 22 are simply temporarily removed to provide adequate access to the mould cavity.

The outer casing 10 is provided with a second inner cylindrical surface 10b which is of greater diameter than the inner cylindrical surface ltla and is axially displaced from the latter. Within this portion of casing 10 are located those components by which the necessary isostatic moulding pressure is generated in timed relation with rotation of the rotor body. These include a cam ring 25 which, as shown in FIG. 3 is held in the desired position of adjustment by two diametrally opposed set screws 26 and lock associated nuts 27. Set screws 26 are threaded through openings in the wall of casing 10 and enable the cam ring 25 to be adjusted eccentrically in relation to the axis of rotation of the rotor body 13 and casing 10 by backing off on one set screw while simultaneously advancing the other. The outer periphery 25a of cam ring 25 is circular as is also the inner periphery 25!) but the latter is located eccentrically to the outer periphery so as to develop a cylindrical cam track for actuating the piston element of each pump associated with each moulding cavity. Each pump is comprised of a pump cylinder 28 established by a bore extending radially inward of the rotor body 13 and a piston 29 within this cylinder. The upper end of each piston 29 terminates in a yoke 30 which is bored transversely of the piston axis at 31 for receiving a shaft 32, the shaft projecting from each side of the yoke for mounting cam rollers 33. These rollers are retained on the shaft by split retaining rings 34 which snap into place in grooves provided on the shaft to prevent any axial movement. The cam rollers 33 engage the inner periphery 25b of cam ring 25 as shown in FIG. 3, and since this inner periphery is eccentric to the axis of rotation of the rotor body 13 is will be evident that as the rotor body is revolved, each pump piston will be caused to move radially inward within its cylinder. The entire annular cavity 35 within which are located the cam ring 25, pistons 23 and their cam rollers 33 is always completely filled with oil, and an oil reservoir 36 with nipple 36a is mounted on the upper side of casing 10 and communicates with the cavity 35 through a feed bore 37 which extends through the wall of the casing and the Wall of the cam ring.

An axially extending oil channel 38 leads from the radially inward end of each pump cylinder 28 to the left end of the rotor body 13 where it is closed off by a screw plug 39. This is provided for bleeding off any air which may be present in the fluid circuit. Leading from oil channel 38 is a second channel 40 which terminates in the annular space 19 between the mould cavity 14 and the back-up member 17 for the elastomeric sleeve 16. Thus, as the body member 13 is rotated and piston 29 driven radially inward, the cam-derived pressure on piston 29 will be transmitted through the oil in the cylinder below it through channels 38 and 40, and thence effect a corresponding isostatic, radially inward directed pressure on the elastomeric moulding sleeve 16 thus compessing the powdered mould material M radially inward against the core 15 to thus mould the powder into article form as determined by the respective configurations of the elastomeric member, and core, if any.

As shown in FIG. 1, the rotor body 13 is mounted for rotation by means of anti-friction bearings 41, 42 located respectively at the opposite ends thereof, and the rotor body is assembled within the outer casing by an annular end plate 43 in which the bearing 42 is received, this end plate being removably secured to the end of the outer casing by a plurality of machine screws 44 arranged around the circumference of the end plate. Oil seals in the form of O-rings 45 are provided wherever needed to prevent loss of oil and pressure from the moulding apparatus. Thus, O-rings are provided on the rotor body at each side of the mould cavities 14, another O-ring is provided between the end face of the casing 10 and the inner surface of end plate 43, and still another O-ring is provided at the inner periphery of the annular end plate 43 which faces a cylindrical portion of the rotor body at the axially outer side of bearing 42.

The right end of the rotor body 13 as viewed in FIG. 1 terminates in a splined shaft 46 for coupling the rotor body with any conventional driving means therefor, not illustrated.

Each pump, cylinder 28 and piston 29, is located in radial alignment with its corresponding mould cavity, and the eccentricity of the ring-shaped cam surface 25b is correspondingly oriented such that a maximum, isostatic mould pressure is reached upon completion of a rotary movement of the rotor body 13 in a clockwise direction as indicated by the arrow, as viewed in FIG. 3, through from the mould filling position shown in FIG. 1 to the dashed line position shown in FIG. 3. Further r0- tation through another 90 allows the piston to retract radially outward to its original position by gravity, thus relieving the pressure.

It is believed that the principle of operation of the improved isostatic moulding press will be evident from the preceding detailed description. However, one complete cycle of operation with respect to one of the mould cavities will now be described in detail.

With the rotor body 13 in the position shown in the drawings, and assuming a clockwise direction of rotation as viewed in FIGS. 2 and 3, mould cavity C1 is situated in the refill position at the top of the press whereas mould cavity C2 is situated in the compact-discharge position at the bottom of the press. Consequently, the finished compact B will have been released from cavity C2 and cavity C1 is being re-filled with the powdered moulding material from the inlet hopper 11. Assuming a continuous rotation of the rotor body 13, the rotative speed will, of course, be so correlated to the rate at which the powdered material can enter the mold cavity that the cavity will have been completely filled up to a level defined by the circumference of the rotor body by the time the rotor body has rotated to the position where top opening to the mould cavity has 'been shut off completely from the discharge mouth of the material inlet 11. The mold cavity is thus completely filled and closed at such time, and further rotation of the rotor body serves to progressively build the hydrostatic force within cylinder 28 as piston 29 is forced radially inward by the cam action effected as between the cam follower rollers 33 and cam surface 25b. This hydrostatic force is transmitted through channels 38, 40, 19 and 18 to the elastromeric moulding member 16 and thence to the powdered moulding material. The hydrostatic moulding force applied isostatically and radially inward against the moulding material so as to compress and compact it reaches its maximum when the rotor body 13 has been displaced 90 from the position depicted. Further rotation of the rotor body through the next 90 permits the piston to retract to its original position, relieving the pressure and permitting the elastomeric sleeve :16 to return to its original position against the back-up support member 17. The interior of cylinder 28 radially inward of the end of piston 29 is filled by oil flowing through the passages 47 which permit the piston sealing ring to be by-passed When the piston is in its outermost radial position which is the position depicted in FIG. 1. When the mold cavity G1 has thus been displaced through a total of 180", it is thus aligned with the bottom discharge opening 12 whereupon the finishedcompact B drops out of the press into a suitable receptacle. When mould cavity C1 has reached the discharge position, mould cavity C2 will have been rotated into the refill position at the top of the press. Thus, a complete moulding operation for each mould cavity takes place for each 180 rotation of the rotor body 13.

In conclusion, it will be seen that the improved rotary type isostatic moulding press has the advantage of a relatively high production rate and which is achieved by means of a relatively simple mechanical arrangement involving use of a built-in hydrostatic pump of the piston'cylinder type and wherein the hydrostatic pressure may be adjusted and simply controlled by means of an adjustable cam ring which together wth follower means therefor serves to regulate the stroke of the piston and hence also the pressure.

It will also be understood that the moulding press construction which has been described and illustrated is to be considered only as typical of the inventive concept and hence various immaterial changes may be made in the construction and arrangement of the component parts without, however, departing from the spirit and scope of the invention as defined in the appended claims. Also, While it has been explained that the rotor body can be rotated continuously, it is also possible to operate the rotor in an intermittent manner in steps of 180 with a dwell period at the position of the rotor indicate in FIG. 2 sufficient to permit the necessary re-fill of the mould cavity.

I claim:

1. In an isostatic moulding press, the combination comprising a casing, a rotor body mounted for rotation within said casing, at least one mould cavity extending inwardly from the periphery of said rotor body, an elastomeric moulding member disposed within said mould cavity, an inlet extending through the wall of said casing for filling the interior of said elastomeric moulding member with moulding material when said mould cavity and inlet are in radial alignment, an outlet extending through the wall of said casing for permitting discharge of moulded articles when said mould cavity and outlet are in radial alignment, a hydrostatic pump comprising a liquid filled cylinder within said rotor body and a piston, a liquid feed channel extending through said rotor body from said cylinder to the exterior surface of said elastomeric member, a stationary cam track and a cam follower cooperative with said cam track and which is connected to said pump piston for actuating it to build a hydrostatic pressure within said pump cylinder as said rotor body is rotated from the mould filling position, said hydrostatic pressure being transmitted from said pump cylinder through said feed channel to the exterior surface of said elastomeric member thereby to product an isostatic moulding pressure directed inwardly against the mould material within said elastomeric memher.

2. In an isostatic moulding press, the combination comprising a casing, a rotor body mounted for rotation within said casing, at least one mould cavity extending inwardly from a cylindrical portion of the periphery of said rotor body and which rotates substantially in contact with a corresponding cylindrical portion of the inner wall of said casing, an elastomeric moulding member disposed with said mould cavity, an inlet extending through the wall of said casing for filling the interior of said elastomeric moulding member with moulding material when said mould cavity and inlet are in radial alignment, an outlet extending through the wall of said casing for permitting discharge of moulded articles when said mould cavity and outlet are in radial alignment, a hydrostatic pump comprising a liquid filled cylinder and piston, a liquid feed channel extending through said rotor body from said cylinder to the exterior surface of said elastomeric member, said cylinder extending inwardly from the periphery of said rotor member, a stationary cam track surrounding said pump piston, and a cam follower cooperative with said cam track and which is connected to said pump piston for actuating it in a radially inward direction to build a hydrostatic pressure within said pump cylinder as said rotor body is rotated from the mould filling position, said hydrostatic pressure being transmitted from said pump cylinder through said feed channel to the exterior surface of said elastomeric member thereby to produce an isostatic moulding pressure directed inwardly against the mould material within said elastomeric memher.

3. In an isostatic moulding press, the combination comprising a casing, a rotor body rotatably mounted within said casing, said rotor body having a first cylindrical surface portion of substantially the same diameter as a first cylindrical surface portion of the inner wall of said casing such that said two cylindrical surface portions engage each other as said rotor body rotates, at least one mould cavity extending inwardly from said cylindrical surface portion of said rotor body, an elastomeric moulding member disposed within said mould cavity, an inlet extending through the wall of said casing for filling the interior of said elastomeric moulding member with moulding material when said mould cavity and inlet are in radial alignment, an outlet extending through the wall of said casing for permitting discharge of moulded articles when said mould cavity and outlet are in radial alignment, a hydrostatic pump comprising a liquid filled cylinder and piston, a liquid feed channel extending through said rotor body between said cylinder and the exterior surface of said elastomeric member, said cylinder extending inwardly from a second surface portion of said rotor body axially displaced from said first cylindrical surface portion, said second surface portion of said rotor body being located in spaced relation to said inner wall of said casing to establish a chamber therebetween, a stationary cam ring having an inner cam track surrounding said second surface portion of said rotor body within said chamber, and a cam follower co operative with said cam track and which is connected to said pump piston for actuating it in a radially inward direction to build a hydrostatic pressure within said cylinder as said rotor body is rotated from the mould filling position, said hydrostatic pressure being transmitted from said cylinder through said channel to said exterior surface of said elastomeric member thereby to produce an isostatic moulding pressure directed inwardly against the mould material within said elastomeric member.

4. An isostatic moulding press as defined in claim 3 wherein said inlet and outlet are disposed apart in the wall of said casing and in vertical alignment.

5. An isostatic moulding press as defined in claim 3 wherein said inlet and outlet are disposed 180 apart in the wall of said casing and in vertical alignment, and wherein two mould cavities spaced 180 apart are provided in said rotor body, each said mould cavity having a hydrostatic pump individual thereto, said pumps and the cam followers connected to the pistons thereof being likewise displaced 180 apart such that a complete moulding cycle for each mould cavity is established for each 180 rotation of said rotor body.

6. An isostatic moulding press as defined in claim 3 and wherein said casing is provided with an opening in addition to said inlet and outlet extending through the wall thereof in axial alignment with said mould cavity, said opening being closed by a removable plug and which serves to permit one elastomeric moulding member and associated moulding elements to be substituted for another within said mould cavity.

7. An isostatic moulding press as defined in claim 3 and which includes a removable end plate closing one end of said casing to permit installation of said rotor body, hydrostatic pump, cam ring and cam follower.

8. An isostatic moulding press as defined in claim 3 and which further includes means for adjusting the eccentricity of said cam ring in relation to the axis of rotation of said rotor body thereby to effect a correspond- 8 ing adjustment in the magnitude of the hydrostatic pressure developed by said pump.

9. An isostatic moulding press as defined in claim 3 and wherein said chamber as well as said cylinder is filled with the liquid medium utilized to develop said hydrostatic pressure.

10. An isostatic moulding press as defined in claim 3 and which further includes an air bleed channel in communication with said feed channel, said air bleed channel leading to the exterior of said rotor body and terminating in a removable closure member therefor.

References Cited by the Examiner UNITED STATES PATENTS 2,152,738 4/1939 Jetfrey. 2,287,675 6/1942. Fair et al. 18-21 2,799,048 7/1956 Stern et al. l8--2l 3,014,240 12/1961 Burt 1821 3,034,191 5/1962 Schaefer et al. 3,038,199 6/1962 Barton et al. 18-5 X 3,103,699 9/1963 Gerard et al.

WILLIAM J. STEPHENSON, Primary Examiner. 

1. IN AN ISOSTATIC MOULDING PRESS, THE COMBINATION COMPRISING A CASING, A ROTOR BODY MOUNTED FOR ROTATION WITHIN SAID CASING, AT LEAST ONE MOULD CAVITY EXTENDING INWARDLY FROM THE PERIPHERY OF SAID ROTOR BODY, AN ELASTOMERIC MOULDING MEMBER DISPOSED WITHIN SAID MOULD CAVITY, AN INLET EXTENDING THROUGH THE WALL OF SAID CASING FOR FILLING THE INTERIOR OF SAID ELASTOMERIC MOULDING MEMBER WITH MOULDING MATERIAL WHEN SAID MOULD CAVITY AND INLET ARE IN RADIAL ALIGHMENT, AN OUTLET EXTENDING THROUGH THE WALL OF SAID CASING FOR PERMITTING DISCHARGE OF MOULDED ARTICLES WHEN SAID MOULD CAVITY AND OUTLET ARE IN RADIAL ALIGHMENT, A HYDROSTATIC PUMP COMPRISING A LIQUID FILLED CYLINDER WITHIN SAID ROTOR BODY AND A PISTON, A LIQUID FEED CHANNEL EXTENDING THROUGH SAID 